P0170Powertrain
Powertrain · SAE
Fuel Trim Malfunction – Bank 1
Meaning
The ECU detected that the short-term and long-term fuel trim corrections on Bank 1 have exceeded the adaptive range. The system is unable to compensate for the air/fuel ratio error detected on that bank.
Common causes
- Vacuum leak at the intake manifold or connecting hoses
- Dirty or faulty MAF or MAP sensor
- Clogged or degraded fuel injectors
- Fuel pressure deviation (too low or too high)
- Contaminated or aged lambda sensor on Bank 1
- Clogged air filter or air leak upstream of the MAF sensor
Symptoms
- Malfunction indicator lamp (MIL) illuminated
- Increased fuel consumption
- Reduced or erratic engine performance
- Rough idle
- Possible smell of unburnt fuel from the exhaust
Severity
Moderata: The vehicle may remain in temporary use, but the issue can cause catalytic converter damage and increased emissions if not resolved.
What to do
- Read and record all stored fault codes and live fuel trim data
- Visually inspect vacuum lines, hoses, and electrical connectors on Bank 1 for leaks or damage
- Clean the MAF sensor with a dedicated cleaner spray and verify its operation
- Check fuel pressure at idle and under load using a pressure gauge
- Test injector operation and lambda sensor function; replace defective components